This invention relates to a scale having a load bed which is supported, directly or indirectly by load supporting members on one or more load levers which transmit force from the load bed to a measuring device.
In a platform scale having a flat load bed and a measuring device acted upon by a load lever, generally the load bed is supported on the load lever system at its four corners. The quality of support appreciably affects the measuring properties of the scale, and the strength and sturdiness of the scale in operation.
Known types of load supporting members for transmitting forces acting on the load bed to the load lever system are the swinging-lever hanger type, the spherical support type, and the swinging-lever upright type. In all these types of load supporting member, the support elements are generally made of metal. The contact surfaces must accordingly undergo costly machining (grinding and polishing) and require frequent maintenance in the form of greasing and cleaning. In addition, in all cases the support in the vertical direction is rigid, so that vertical impacts which can occur, for example, when a load is set down abruptly on the load bed, are transmitted undamped to the load lever. Such sudden loading of the load lever system can cause damage. In addition, deflections of the load bed in the horizontal direction can give rise to a persistent rocking of the load bed, which makes operation difficult.
It is known to employ a cylindrical elastomeric piece in a load supporting member (load upright) with the elastomeric section sandwiched between metal discs comprising end members of a three-layer load upright structure. In this arrangement, one end member is a flat metal plate rigidly attached to the load bed, and the opposite end member is in the form of a metallic cone which rests in a matching depression in the load lever system. In such a load upright attached to the load bed (or to the load lever system) at least at one end of the load upright, the stiffness in the vertical direction is not appreciably greater than the stiffness in the horizontal direction. If a relatively soft load upright is used, vertical compression of the load bed is too great; and if a relatively hard load upright is used, there is little shock absorption in the horizontal direction, so that side forces on the load bed are transmitted to the load lever system via the load upright, and may damage the load lever system.
Accordingly, an object of the present invention is to provide a load supporting member (load upright) construction which affords greater protection for the load lever system of the scale than in known arrangements, and which is simple and easy to manufacture and maintain.